In the automatic industrial door and overhead door industry, there is a concern that, once activated, a moving door may injure persons or property inadvertently in the path of the door. See Richardson's U.S. Pat. No. 5,964,058, which uses an electrical contact to trip a relay to reverse the motion of the door. More commonly, light beams are used at levels where they are apt to be interrupted by pedestrian traffic or vehicles such as automobiles, trucks, fork lifts and the like in order to prevent injury or damage to the vehicles. Safety light or other radiation beams are also used for automatic household garage door opening systems, to assure that the door will stop or reverse its downward motion if the area beneath it is suddenly occupied by a toddler, for example. Halting or reversing the motion of the door without touching the object or person breaking the beam has proven to be an effective safety procedure.
Typically the beam generators and the photocells are installed in metal or other rigid brackets in the door jambs or on adjacent walls. See, for example, Mathis U.S. Pat. No. 6,209,262, Duhame U.S. Pat. No. 5,285,136, Catlett et al U.S. Pat. No. 4,006,392 (sliding door), Boetsch et al U.S. Pat. No. 5,166,681, Harvey U.S. Pat. No. 6,179,036 (light beam for a truck door) and Alexander U.S. Pat. No. 5,459,963. The beam may also be mounted within a flexible tube on the bottom of a vertically moving door. See Miller U.S. Pat. No. 5,728,984, and Strand U.S. Pat. Nos. 5,079,417 and 5,399,851.
Little attention has been paid in the industry, however, to the vulnerability of the photocell supports and supports for light beam or other radiation devices to damage from errant vehicles and other moving objects. Particularly where the light beam projector, photocell, microwave or infrared device or photo receptor holder must protrude from the door jamb, wall, door or other base, the holder is highly likely to be damaged at some point over a period of time. Fork lifts, for example, can be difficult to steer and often contain awkward loads which may accidentally impact the light beam generator or receptor. Even in household garage applications, the support for a light beam generator or receptor cell may be damaged not only by automobiles, but possibly by lawnmowers or other utensils typically stored in the garage.
In U.S. Pat. No. 4,953,608, Larsson describes a displaceable photocell support arm. The arm is slidable within a sleeve on the underside of a door, so that when a base member or abutment on the lower side of the photocell hits the floor, the support arm can slide into the sleeve. While the support arm is displaceable, it is not especially adapted for protection against a transverse impact, and in fact a transverse blow would impair its movement by rendering it incapable of sliding in the sleeve.
Myeress, in U.S. Pat. No. 3,864,837, shows a shroud for a light beam generator. The shroud provides a mounting and a pivot axis for the light beam generator. The device is used in surveying.
The Larsson and Myeress devices mentioned above will not solve the problem of damaged supports for photocells and beam projectors. It must be recognized that the light beam must be directed at the photocell and the photocell must be oriented to receive the light beam. If either is twisted so there is no communication between them, the system becomes totally inoperable, completely defeating any planned safety measures.
Motion and presence detectors used in doorways do not necessarily require separate emitters and receivers on opposite sides of the doorway. As is known in the art, microwave, infrared, and ultrasound emitters can be designed and used to detect a disturbance in a background pattern of reception. For such installations, a single radiation transceiver on one side of the doorway or entrance will suffice. The transceiver will emit, for example, a microwave signal in a direction transverse of the doorway, receive a background pattern represent the area in its usual vacant state, and transmit such a pattern to a microprocessor or other device for comparison to a pattern received when the picture is disturbed by the entrance of a person or object. Such a transceiver, using light, microwave, infrared, ultrasound, or other radiation, may be mounted in a single holder near the door, and is also available for use in our invention.
I am not aware of any support or mounting for a photocell, light beam transmitter or other beam or radiation transceiver which can continue to operate even if it is twisted or bent.